1985 baby Marquis 3.8 V6 idles high

[Illousion]

Hey guys!
It's been an eternity since I was on here, and I know this really is not a fox body ford forums but since my car has CFI I figured I'd give it a shot here. I've got a 1985 Mercury Marquis with the 3.8 V6 with CFI. It idles high. I don't have a tach in the car nor do I have access to an auxiliary tach but it idles high. Now right after starting it it's at it's highest and after like ten-fifteen seconds it goes down a little bit but it's still high. When I put it in gear it requires quite a lot of pressure on the brake pedal for it to not move and the motor idles pretty rough with the trans in gear. When I put the trans back in Park the idle goes up to its highest again and does not go down.

Since the idle goes down a little after a few seconds I doubt the idle control valve. The car had sat since 2007 when I bought it in November and I've yet to give it a proper rotor/cap/plugs/wires service but I figure some sort of vacuum leak somewhere since these cars have miles of vacuum lines everywhere. But where do I start looking? Do you guys think it could be anything else causing the high idle?

Thanks in advance boys.

[L1011tristar17]

I had the same problem in my car and it turned out to be a vacuum leak. I know that some shops have a smoke machine that they attach to the vacuum lines and it blows smoke out of wherever the leak is. Another thing you could try is spraying soapy water over the lines while the engine is running. If you see bubbles that means that air is escaping from that line. Some people spray carb cleaner instead but that could be dangerous. Good thing that vacuum lines are relatively cheap and it wouldn't hurt to replace any of them that are already old and dry-rotted.

It also turned out that I had installed new coolant temp sensors and the computer had to "learn" them. This meant I had to unplug the battery for fifteen minutes. Don't know if CFI cars work the same way.

[gadget73]

Is the high idle linkage sticky? The CFI throttle body has a mechanical high idle setup very much like a choke. If that is gummy, it won't come off of high idle. The vacuum lines need at least an inspection and probably at least partial replacement but make sure the mechanical bits aren't sticky first.

[Illousion]

Figured I'd update you guys, it might be of help to someone.
After some time of not really getting anywhere I learned that these cars have the EEC-IV system that allows you to pull error codes. It gave me code 31 or 32, can't remember now but the code was from the EGR valve. After some studying on the net someone suggested the EVP-sensor located on top of the EGR. I removed it and that seems to solve the problem, sort of. With it removed/unplugged it idles at 850-900rpms. I've ordered a new EVP-sensor but it has not arrived yet so this is a temporary solution.
Now I do say sort of because the problem isnt 100% sorted out. Is the rpms I'm getting normal for a car like this or is it still a bit high? Besides from that, now that it's at lower rpms I've found out that it idles poorly. The engine shakes a bit and if you listen to the exhaust note the car caughs at idle (do note that I've changed the plugs, wires etc and that stuff is fine). From quick googling vacuum leaks are suggested, but could it be anything else? I've checked alot of the vacuum lines and changed a few and changed the MAP-sensor. There are three things though that I wonder about;
- Under the EGR-valve there's traces of exhaust leaks, black marks. Can this be something related to this?
- When the car idles and I lie under the dashboard listening it sounds like there's a leak somewhere. The fan is off and so is the stereo. I tried juggeling the vacuum lines I could see but it changed nothing.
- The parking brake is released when placing the trans in Drive, but not Reverse. Could there be some vacuum leak there? There's some sort of vacuum canister where the pedal is but it only has one large vacuum line going to it.
Please help me out, it feels like I've hit a dead end here and I don't know what the next step is.

[sly]

V6 should be around 800.

Sent from Blaster coming at ya from Autobot City.

[gadget73]

If you see carbon chooching around the EGR valve, the gasket under it is probably shot. It may be sucking air through there, and that would make it idle silly. Pull that all out and clean it. If you have the type of EGR spacer that is a seperate part underneath of the CFI unit, I'd pull the CFI unit off, remove the EGR spacer for a deep clean, and then re-assemble with new gaskets. I don't know if the 3.8 used that setup though. it might just be cast into the intake like some were. Either way, clean what you can when you pull the valve off to change the gasket. See if the valve holds vacuum too while you're in there. you should be able to apply vacuum and see it open, and it should stay open. If it drifts closed, its leaky and needs to be replaced.


Sounds like the vacuum release for the parking brake may be goofy. If you hear air sucking from inside the car around the brake pedal, thats probably it. That valve should live on the inside, somewhere on the steering column down near the firewall. I don't know the undersides of the fox car dashboard, but if its like the full size cars, its probably a curved white plastic thing with 2 hoses going to it. If its hissing, unhook the vacuum line and plug it to see if anything changes. Don't know if that valve can be had new or not.

Does the high and regular idle circuit work normally? When cold, you should have to pump the pedal once to set the high idle cam before starting. After it warms up a bit, a quick pump of the pedal should drop the high idle cam out and return it to regular idle. High idle cam is on the passenger side of the CFI assembly, low idle is the dashpot on the driver's side. If the choke heater is unhooked or not working, it will not drop from high idle. If the linkages are gummy, it won't work right either. If the alternator isn't the original type and you didn't re-connect the choke heater wire to the stator of the new one, it won't work.